Combined process for converting light and heavy hydrocarbons



1941- E. G. BORDEN 2,265,510 COMBINED PROCESSFOR CONVERTING LIGHT AND HEAVY HYDROCARBONS Filed NOV. 17, 1938 88 Sui 82 ABSORBER CIONDENSEYR .STABIZER I18 If: m 105 III. 105

IACCUMULATOR -112 COOLER 25 CATALYTIC CHAMBER Patented Dec. 9, 1941 2,265,510 COMBINED PROCESS FOR CONVERTING LIGHT AND Edmund G.

Cities Service Oil Co corporation of Pennsyl Application November 17, 1938, Serial No. 241,031 g 9 Claims. ('01. 196-9) This invention relates to a combined process for converting hydrocarbons such as normally,

gaseous hydrocarbons and liquid hydrocarbons into a gasoline-like product suitable for ,use in internal combustion engines. I

Considerable progress has been-made in the conservation of the low molecular weight hydrocarbons by polymerizing them into hydrocarbons suitable for motor fuels and other products, but no apparent attempt has been made to save the C: hydrocarbons, ethane and ethylene. TheCa and C4 hydrocarbons are recovered in some stabilizing operations and such hydrocarbons" sent to a polymerization unit to be converted into higher boiling products.

The primary object of the present invention is the provision of an improved process for combining the polymerization of normally gaseous hydrocarbons such as C2, C and C4 hydrocarbons with the conversion of oil cracking stocks.

A further object of the invention is to provide a combined conversion process which is particularly suited for the substantially complete conversion of various types of hydrocarbons into gasoline motor fuel.

In general the improved process of the present invention involves the steps of subjecting a heavy hydrocarbon to a cracking temperature in the vapor phase, the cracking of a normally gaseous hydrocarbon to convert it substantially to unsaturated constituents, the mixing of the hydrocarbons from these two conversion steps, and subjecting the resulting mixture to conditions for promoting polymerization and alblation reactions for the production of a product containing a very high percentage of aromatic hydrocarbons. The improved process also includes the refining of the conversion products and particularly the recovery of the unconverted Cr, C: and C4 hydrocarbons and the return of such hydrocarbons I free of hydrogen and methaneto the conversion operation.

Various other features, objects and advantages of the improved process of the present invention will be apparent to those skilled in the art from thefollowing more-detailed description of the in-' vention taken in connection with the accompanythe drawing in which: I

The single figure is a conventional elevational of an improved cracking unit particularly adapted for carrying out the process. The heavy hydrocarbon material to be proc-' essedin-accordance withthe features of the invention and which may comprise crude oil, topped HEAVY HYDBOCARBONS Borden, little Neck, N. Y., assignor to mpany,-New York, Y., a

into the apparatus shown in the drawing through a line 2 (lower left hand corner of the drawing) and forced by means of a pump 4 at a pressure of from 500 to 600 lbs. persquare inch through a line 6 and a vaporizing coil 8 mounted in a pipe still furnace Ill. The oil passing through the coil 0 is heated to a temperature of from 800 to 900 E, which is suiiicient to vaporize substantially all of the constituents boiling within the gas-oil range as well as lower boiling hydrocarbons. The resulting heated hydrocarbon material is passed from. the coil 8 through a'line l2 into a vapor separator H in whichvapors are separated from unvaporized oil constituents and conducted at a pressure of from 350 to 400 lbs. per square inch through a vapor line 16 and a cracking coil 48 mounted .in the pipe still furnace l0. The relatively heavy hydrocarbon vapors introduced into the coil I! are heated to a temperature of from 925 to 1050 F. and substantially cracked to produce a maximum of unsaturated hydrocarbons including some olefin gases of lower boiling point than gasoline. In this coil no attempt is made to convert the heavy hydrocarbon vapors to gasoline, but the temperatures for cracking are controlled to cause such a rearrangement or breaking of the hydrocarbon molecules that they will be prepared for a later ,cracking and polymerization reaction. The cracked products formed in the cracking coil I! are conducted through a line 20 and passed into a polymerization furnace 22. v

' The light normally gaseous hydrocarbons to be converted in accordance with the features of the 3 present invention are at least partially derived from the process and conducted through a line 23 at a pressure of from 400 to 550 lbs. per square vinch into a heating coil 24 mounted in a pipe still furnace 25. Inthis furnace the normally gaseous hydrocarbons comprising substantially only Ca, C: and C4. hydrocarbons are rapidly heated to a temperature of from 950 to 1200 1",, to break up the saturated hydrocarbons and produce a maximum of oleflns. A Ordinarily it is not possible to obtain more than about or of oleflnsby thermal conversion in'the coil 24. The highly heated hydrocarbon mixture is therefore conducted through a'transfer line 20 into the lower portion of a catalytic chamber 21 where the heated hydrocarbons are brought in contact with a 'dehydrogenating catalyst such as chromic oxide or chromium trioxide which will give a mixture containing from 60% to unsaturated hydrocarbons. This mixture of-olefln hydrocarcrude or other heavy petroleum oil, is introduced bons-isconducted through a valved line 28 into the line 26 and directly mixed with the high te perature cracked products from the cracking coil l8. If desired, any part or all of the highly heated gaseous hydrocarbons discharged from furnace 25 through the line 26 may be by-passed through a valved line 30 into the line 26 to mix with the unsaturated hydrocarbons from the reaction chamber 21. v

The mixture of hydrocarbons from cracking coils l8 and 24, and which preferably comprises at least 50% by weight of normally gaseous hydrocarbons, is conducted into the polymerization furnace 22 and passed through a series of heating coils 32 arranged in parallel as illustrated diagrammatically in this furnace. The use of these parallel coils permits the maintenance 'of a I relatively long, time polymerization reaction withplace in the chamber 21 may advantageously comprise the treatment of the hot gases with a catalytic material such as a mixture of magnesium oxide and chromium trioxide, or chromic oxide, or aluminum oxide and chromium oxide, and such oxides or mixtures of oxides may be deposited on fullers earth and arranged in vertically spaced trays in the chamber 21. The gases are held at a temperature of from 1050" to l200 F. as they emerge from the coil 24 and are preferably held at a temperature of approximately 1100 I. These gases are under the pressure maintained in the coil 24 which may vary from 300 to 450 pounds. It is economically desirable to maintain the same pressure in the chamber 21 as that existing at the outlet of the coil 24 and accordingly the temperature of the entering gases is maintain ed high in order to promote the reaction. The conversion of paraflins to oleflns is more rapid under lower pressures, but in view of the fact that it is desirable to maintain the same pressure in chamber 21 as at the outlet of the coil the temperature is preferably increased to give the desired dehydrogenation reaction. If necessary the chamber 21 may be'heated exter-. nally to maintain the desired temperature there- The unvaporized heavy hydrocarbon oil constituents separatedout in the separator M are normally withdrawn through a valve line 31 and used as fuel'oil. Ifthe oil residue has not been subjected to cracking conditions for a'suflicient period in coil 6 to properly break the viscosity of the heavy hydrocarbons, higher temperature cracking conditions. In case the liquid material is withdrawn from the that of coke deposition by intimate contact with I a relatively cool fluid introduced through a spray nozzle 42. The fluid introduced through I the nozzle 42 may be water but preferably oil, such as concentrator gas-oil or other heavy oil, sup-- plied through a line 44. Where the viscodty of the heavy oil constituents collected in the bottom of the separator i4. is suitable for use as fuel oil this hydrocarbon material may be used in part as a que'nchingmedium for the nozzle 42 by passing,

it through a valved connecting line 46.

The cooling effected in the lower portion of the reaction chamber 36 as the hot products enter,

the funnel 46 is preferably sufficient to condense substantially all hydrocarbons boiling above that of ordinary gas oil. Any such condensate together with the fuel oil constituents introduced into or formed in the chamber 36 are discharged with the uncondensed vapors through the funnel 46 into a separating chamber 46 and then conducted through a valved line 56 into a low pressure concentrator 52. A pressure of approximately 225 lbs. per square inch is maintainedin the reaction chamber '36 and separator 46, so

that considerable distillation may be effected in the concentrator 62 by reducing'the pressure on the liquid oil constituents passing through the line 56. The vaporization however, is preferably this oil is subjected to bottom of the separator I 4 through line 31 and a valved line 36 and introduced into the midportion -of the reaction chamber 36, so that the heavy hydrocarbons are brought into contact with the high. temperature vapor and gas products introduced through the line 34. The resulting mixture of products pass downwardly through the chamber 36 and as the products approach the inlet to a funnel 46, they are substantially instantly reduced in temperature to a point below v tillate.

controlled, so that a fuel oil of proper consistency will be obtained from the concentrator. This is withdrawn to storage through a valved line 64.

Theva'pors produced in the concentrator pass through a vapor line 56, are condensed by a condenser mounted therein and collected in an accumulator 58 from which any uncondensed gas is discharged through a valve controlled gas line whichis used to maintain the desired back pressure on the concentrator 52.

The vapors remaining uncondensed in the conversion operation and separated out in the chamber 48 are conducted through a vapor line 66 into a dephlegmator or fractionating tower 62. The vapors in the line 60,5may be fm'ther cooled by introducing cooling fluid from the line 44 directly into the line 66 through a valved line 64, but the cooling should not be carried to-such a low temperature that the gasoline boiling point material will not all be driven overhead from the tower 62. The vapors introduced from the line 66 into the lower part of the tower 62 are fractionated, and additional cooling may also be effected in the lower part of this tower by utilizing all or a portion of the distillate from the accumulator 56, this distillatebeingwithdrawn from the accumulator through a line 66 and forced by means of a pump mounted therein through a valved connecting line '66 into the lower .part of the tower 62 above the point of vapor introductionfrom the line 66. Vapors entering the tower will be brought in intimate contact with any of the distillate from the line 66 and vaporize any of the low boiling gasoline hydrocarbons which may be present in the dis- The fractionating operation carried out in the tower 62 is preferably controlled so that all high boiling material above the boiling point of gasoline will be condensed. This condensate, together with the distillate from the accumulator 56, and conducted through valved lines 66 or 66, is withdrawn from the tower through a line 16 and forced by means of the pump mounted therein into the line 6 through which it is-supplied as charging stock for the vaporizing coil 6. The gasoline boiling point vapors-and unconthrough a valved vapor line 88 82 above the point of introdensable gases from the conversion operation are separated out in the tower 82 and are conducted through a vapor line 12, subjected to condensing conditions in a condenser mounted therein, and discharged into an accumulator II in which the uncondensed normally gaseous hydrocarbons are separated from the gasoline boiling range condensate. in the accumulator I4 is withdrawn through a line I6 and forced by means of a pump mounted therein through a valved line 18 and a heat exchanger 88 mounted therein into the mid-portion of a stabilizer tower 82.

The gases separated out in the accumulator I4 comprise hydrogen, methane, the C2, C3, C4 and some C5 hydrocarbons which are produced in the conversion operation or remain unconverted therein. This mixture of gases is withdrawn from the accumulator 14 through a valved line 84 and placed under a pressure of about 600 lbs. per square inch by a compressor mounted therein, cooled in a cooler 88 and discharged in-- to the lower portion of an absorber 88 where the gases are subjected to the absorbing action of a suitable absorption oil for the recovery of the C2 and higher hydrocarbons substantially free of methane and hydrogen, the latter gases being discharged through a valved line 88 The cooling of the gases from the compressor in the cooler 88 may be eflected at least in part by heat exchange with gasoline from the line I6 which may be conducted through the cooler in indirect heat exchange with the gases and back into the line 18, beyond the valve mounted therein, as shown.

The absorber 88 includes suitable means such as bubbler trays, for providing intimate contact between thegases'and the absorption oil, andis also preferably provided with cooling coils to increase the absorption eiilciency. The absorption oil used in the absorber 88 may be any oil from a gasoline range but it has been found that better absorption is obtained with the lower boiling oil. This oil is introduced into the absorber under pressure through a line 82, and the rich absorption oil is removed from the bottom of the absorber through a float valve controlled line 94, heated by a heater mounted therein and passed into a still 98 which is used for separating the absorbed normally gaseous hydrocarbons from the absorption oil. The rich absorption any gasoline boiling rangematerial absorbed from the gases and into the mid-portion of the stabilizer duction of the gasoline through the line 18. The

leanabsorption'oil obtained in the still 88 is re-' j line Ill, passed through the Q moved through a heat exchanger 88 to heat the gasoline in the line 18 and then forced by means of a pump mounted in the line Ill through a cooler [82 anda line I" into the upper part of the absorber 88. a gasoline boiling range absorption oil such as a stabilized gasoline or a heavy gasolinejs used the rich absorption oil is preferably conducted directly into the rectification therein along gasoline from the accumulator ll.

The pressure in the absorber maintained at inch and that in pressure, such that the pressure 82 may be maintained in the neighborhoodfof The gasoline collected 7 oil may beheated to a temperature suilicient to drive over these vapors are passed 7 stabilizer 82 and subjected to f with ,the unstable- 88 is preferably 70 from 500 to 600 lbs. per square the still 88 at a slightly lower 8 in the stabilizer Q through a condenser 500 lbs. per square inch. In the operation of the absorber 88 the gases removed overhead through the line 98 in addition to hydrogren and methane may include nitrogen and also some carbon oxygenogases in addition to a small proportion of C2 hydrocarbons. However, the operation is preferably controlled so that as much as possible of the C: hydrocarbons will be absorbed. Under the pressure conditions referred to, the rich absorption oil will be heated .to' a temperature of from 500 to 700? F. in the heater mounted in line 94.

The stabilizer 82 is operated as a rectification column to produce a bottom product comprising stabilized gasoline having the desired vapor pres-.

sure gand containing the requisite proportion of C4 hydrocarbons to give this vapor pressure. excess of the C4 hydrocarbons and the C2 and C3 hydrocarbons are removed over head from the stabilizer through a vapor line I88, passed mounted therein, and the resulting condensate collected in an accumulator to a gas-oil boiling range,

' conducted from ,the

I .fact that at'least 50% ofthe pipestill'fl 111 as the absorption medium in the absorber",

accomplished by dehydrogenation reaction as,

,an 1 oxidation reaction,

I88. Any uncondensable gases separated out in the accumulator I88 are withdrawn through a line H8 and placed under a pressure of about 600 lbs. per square inch sor mounted therein, and passed to the absorber 88 through the line 84. The condensate collected in the accumulator I88 and comprising ethane, propane and butane and the corresponding unsaturated hydrocarbons, is withdrawn through a valved line 2- into a line I, from which a suitable part of the condensate is forced by means of a pump H6 and a line II8 into the upper part of the stabilizer 82, to provide a suitable reflux ratio in the top of the stabilizer, The net pro- "duction of condensate in the accumulator I88 is has type to supply suiiicient suitable pressure into supply I22. stock in the furnace25 will be apparent furnace 28.

.Inplace of the catalytic chamber'l'l 'for thel production of unsaturated gaseous from .th larly the productionof olefln's,;a I

02, C; vand C4 hydrocarbons,

. rb used; genation of the. saturated hydrocarbons may be bon: vapors.

with the. hydrocarbons incrementsand tubes'of the coil 24,

ave r ached P edetermined temperature,

The

by means of a compreslineIIl into the line 23 at a pressure of from 400 to 450 lbs. per square inch the heavy hy-v to. introduce additional- 25. This dai t-ional.stock in the form or gaseous or liquefied P ethane, propane or butane, or a mixtureof-any of these hydrocarbons is introduced under ;a

the line 28 through a-valved I r The necessity-ionising outside; a

o fr m th a entire-material enteritis I 7 the furnace 22=is preferably derivedfrom the hydrocarbons p rtions r I v usingarelatively small pr'o'ji'or -j tion. of .air or oxygen in; treating the; hydrocar-. To utilize -theair for promoting j; distinfl h 11mw the air must be mixed" m ra i e is'preferably introduced into the;

after jthehydrocarbonvapors 1' 1 comparatively small amounts. To accomplish this the air is introduced into the vapor stream through small tubes which project into the tubes of the coil 24. These small tubes are made of nickel or alloy metals and have porous walls through which air in minute streams is forced into the vapor stream by a comparatively high pressure. As shown inthe drawing, air is forced ,by means of a pump.l24 through a line I26 which is connected with a plurality of small tubes I28 which project into the tubes of the pipe coil 24 The small porous tubes extend for a considerable distance into the tubes of the pipe coil so that the air is distributed over a considerable area into the hydrocarbons. It is important that small proportions of air shall be used because the action within the body of hydrocarbons which tends to raise the. temperature. The temperature of the vapors preferably is held sufliciently high so that the oxygen unites with hydrogen to form steam, and oxidation of the hydrocarbons to produce alcohols, aldehydes, ketones and acids is avoided as much as possible. Some oxygen unites with carbon -to form carbon monoxide but this gas is not objectionable.

The polymerization reactions carried out in the furnace 22 and the enlarged reaction chamber 36 are preferably controlled to obtain a rather long time moderate temperature polymerizing action which favors the production of aromatic hydrocarbons. Such polymerization reactions may be substantially exothermic and result in, the prolarge proportion of fixed gas is produced which is composed mainly of hydrogen, methane and C: hydrocarbons. v

It is not necessary however that the process be operated for the production of such high percentages of aromatic hydrocarbons since motor fuels containing from 25% to 60% areentirely satisfactory from the standpoint of fuel value and antiknock properties. When producing motor fuels of this character the gas production is much lower and will of course contain a greater proportion of unconverted C2, Caand C4 hydrocarbons which will be recycled .in accordance with the above outlined process.

Having thus described the invention in its preferred form, what is claimed as new is: 1. In the conversion of relatively light oils into gasoline of relatively high anti-knock value in which Ca. Ca and C4 hydrocarbons remain unconverted in' the operation and are also f'produced therein, the improvement which comprises fractionating the gasoline and lower boiling constituents of the conversion products of the operation from higher boiling hydrocarbons, subjecting gauging the porosity of the ing the separated gases introduction of air promotes an exothermic reduction of a gasoline boiling range product conthe gasoline vapors and lower boiling constituents condensing conditions at a pressure of approximately 200-250 lbs. the condensate from uncondensed hydrogen, methane, C2, 03,04 hydrocarbons, passthrough an absorption with a cool absorption C3 and C4 hydrocarbons excess of 500 lbs. per rich absorption oil into zone in intimate contact oil and absorbing the Ca, therein at a pressure in square inch, passing the astill and vaporizing the C2, carbons from the absorption oil the resulting vapors as such and also the gasoline condensate produced by said condensation into the mid-portion of a high pressure stabilizer maintained at a pressure of approximately 500 lbs. per,square inch, fractionating the gasoline and gases in said'stabilizer to produce a stabilized gasoline having the desired vapor pressure and an overhead iractional condensate comprising a mixture of C2, C3 and C4 hydrocarbons at a pressure of approximately 500 lbs. per square inch, passing said mixture by means of said pressure thereon to a conversion zone and subjecting it therein to a rapid thermal conversion operation to convert said hydrocarbons into a product containing a substantial proportion of olefins and alkyl radicals, and thereafter polymerizing the resulting products with highly heated substantially cracked oil in a polymerization and alkylation zone tfor the production ucts referred to. r

2. In the conversion of relatively light oils as defined ,in claim 1 in which said mixture of C2, C3, and C4 hydrocarbons subjected to rapid cracking conditions for the production of oleiins arealso subjectedto the action of a dehydrogenating agentto materially increase the production of unsaturated hydrocarbons and alkyl radicals, and thereafter passing the resulting mixture containing in excess of 60 percent of unsaturated hydro carbons into said polymerization zone. 3. In the conversion of hydrocarbons into gasoline in which 0:, C3 and C4 hydrocarbons remain unconverted in the operation andare also produced therein, the improvementwhich comprises separating the gasoline and lower boiling constituents of the conversion products of the operation from higher boiling hydrocarbons by fractionation, subjecting the gasoline vapors and lower boiling constituents to condensing conditions at a pressure of approximately from 200 to 250 lbs. per square inch tocondense the gasoline constituents, separating the resulting condensate from uncondensed gases comprising hydrogen, methane, C2, C3, and C4 hydrocarbons, compressing the separated uncondensed gases to a high pressure of approximately 500 lbs. per square inch and passing them in indirect heat exchange with said gasoline condensate to cool the gases, thereafter passing the cooled gases into an" absorption zone in intimate contact with a cool absorption oil, and absorbing tbeCa, Ca and C4 hydrocarbons therein at a pressure of approximately 500 lbs. per square inch, passing the resulting richabsorption oil from said absorption zone into a still and vaporizing the C2, C3 and C4 hydrocarbons from the absorption oil by heating the same, passing the resulting vapors as such and also the gasoline "condensate produced by said condensation after per square inch to condense gasoline constituents, separating the resulting gases comprising Ca and C4 hydroby heat, passing of said conversion prodper square inch, fractionating the gasoline and vapors from said still in said stabilizer to produce a stabilized gasoline having the desired vapor pressure and an overhead fractional condensate -comprising a mixture of C2, C3 and C4 hydrocarbons at a pressure of approximately 500 lbs. per square inch, and passing the hot absorption oil from said still in indirect heat exchange wit'h'said gasoline immediately prior to the introduction of the gasoline into said stabilizer.

4. The process of converting hydrocarbons into a product boiling within the gasoline range and containing in excess of 60% aromatic hydrocarbons, which comprises separately and simultaneously heating and cracking a high boiling hydrocarbon oil and a mixture of C2, C3, and C4 hydrocarbons while passing them in restricted streams through heating zones, heating the heavy hydrocarbon to a temperature of approximately 950 F. to convert thejsame into unsaturated hydrocarbons, heating said mixture to a temperature 01 approximately 1100 F. to produce a high percentage of unsaturated hydrocarbons, immediately mixing the highly heated products from said heating zones and passing the resulting mixture in a stream of restricted cross stabilized gasoline of desired vapor pressure and section through a further heating and polyf merization zone in which the products are interpolymerized and converted into aromatic hydrocarbons, cooling and fractionating the resulting conversion products to produce a vapor and gaseous fraction comprising the. gasoline and lower boiling hydrocarbons and gases, subjecting this vapor mixture to condensing conditions at a pressure of approximately 200 to 250 lbs. per square inch to condense the gasoline hydrocarbons, separating the uncondensable gases from the gasoline condensate and compressing the gases to a high pressure of at least 500 lbs. per square inch, passing the resulting compressed gases into an absorber in intimatecontact with an absorptionvoil and absorbing the C2, C3, and C4 hydrocarbons from the compressed gases, passing the rich absorption oil into a still and vaporizing the absorbed constituents by heat, passing the resulting vaporized constituents as such and also said separated gasoline condensate into the mid-portion of a stabilizer in which fractionation of the gasoline and introduced constituents is effected at a pressure of approximately 500 lbs. per square inch to produce a an overhead condensate comprising C2, C3, and C4 hydrocarbons, and supplying said overhead condensate directly at a pressure of approximately 500 lbs. per square inch as at least a part of the said mixture heated in one of said heating zones. j V

5,. The process of conversion as defined by claim 4 in which said separated gasoline is first passed in heat exchange with said compressed gases, then in indirect heat exchange with hot absorption oil withdrawn from said still, and finally introduced into said stabilizer.

6. The process as defined by claim 4 in which said overhead fractional condensate is'produced at a pressure of approximately 500 lbs. per square inch and conducted directly without further compression into the heating zone for said mixture of C2, C3, and C4 hydrocarbons.

'7. The conversion process as defined by claim 4 in which the highly heated mixture of C2, C3, and C4 hydrocarbons is subjected to'active dehydrogenation with a dehydrogenating agent prior to its mixture with the highly heated high boiling hydrocarbons.

8.'In the conversion of C2, C3, and C4 hydrocarbons as defined in claim 1 in which said gases are-subjected to 'a high decomposing temperature of from 1000" to 1200 F. by an indirect heating of the gas and the introduction of air in small proportions into the gas to promote the production of unsaturated hydrocarbons therein and passing said unsaturated gases into the polymerization and alkylation zone.

9. In the conversion of C2, C3 and C4 hyd1'ocarbons as defined in claim 1 in which said hydrocarbon mixture is subjected to high temperatures by indirect heating and. introducing air in minute quantities at a plurality of points in the path of travel of the hydrocarbons to promote an exothermic reaction in the hydro-- carbon mixture for the production of unsaturated hydrocarbons and alkyl groups and passing said preheated and oxidized mixture into the polymerization zone.

EDMUND G. BORDEN. 

